The formation of reversal dye images in photographic elements is generally old and well known in the photographic arts. In a typical approach, a photographic element capable of forming a multicolor image is imagewise exposed and developed in a black-and-white photographic developer composition. The undeveloped silver halide is next rendered developable by uniform exposure or by nucleation. The remaining silver halide is then developed using a color developing agent so that a positive dye image is formed. Reversal processing has proven quite attractive, since it offers a convenient approach for obtaining a positive dye image using a negative-working silver halide emulsion without the necessity of first producing a negative dye image and then reexposing a second photographic element through the negative dye image. Reversal processing to form positive dye images is widely employed in producing color photographic transparencies.
Commonly assigned, copending application Ser. No. 730,912, filed Oct. 8, 1976, (now U.S. Pat. No. 4,089,685, issued May 16, 1978) of Bissonette discloses a process wherein a peroxide redox amplification catalyst is poisoned by iodide ion. A positive image is produced according to this process in the following manner: A conventional exposed negative-working silver halide element is developed to produce a negative silver image. This negative silver image is poisoned, either during silver halide development or in a subsequent step, by iodide ion. Then, the remaining silver halide is rendered developable. Development of this remaining silver halide results in a positive silver image which can be used to catalyze a peroxide redox amplification reaction.
I disclose in my copending application Ser. No. 770,241, filed Feb. 18, 1977, (now U.S. Pat. No. 4,094,684, issued June 13, 1978) entitled "Photographic Emulsions and Elements" emulsions which contain composite silver iodide crystals and silver chloride crystals joined at epitaxial junctions. By proper selection of development conditions, the silver chloride can be developed in preference to the silver iodide, and the release of iodide ions can thereby be controlled. When the composite crystals are entirely developed, the emulsions can be used to imagewise poison developed silver--that is, the silver formed by development of the silver halide can be poisoned as it is developed by the concurrently released iodide ion. While the use of these emulsions in the process of Bissonette, cited above, provides a method for selectively releasing iodide ion from the emulsion to poison the negative silver image, all of the process steps of Bissonette are still required. That is, the remaining silver halide must first be rendered developable and then developed in order to provide a positive catalytic image.
The formation of positive dye images using a cobalt(III) complex as an oxidizing agent in redox dye image amplification processes is known in the art. Such a process is disclosed in Example 1 of Bissonette U.S. Pat. No. 4,002,477, issued Jan. 11, 1977. In such processes the use of a preformed catalyst is contemplated, with exposure and processing being relied upon to imagewise poison the catalyst in exposed areas. Since the halide ions released by development of exposed silver halide do not effectively poison the preformed catalyst, where a cobalt(III) complex oxidizing agent is employed, it is necessary to incorporate other poison releasing materials. In Example 1 a development inhibitor releasing coupler is employed for this purpose.